Ribbon type flow control device

ABSTRACT

A ribbon type flow control device which provides a variable mechanical advantage. A ball type poppet is removably mounted in a valve seat. A pair of elongated flat resilient ribbons are connected at one end thereof to the ball and fixed at the other end. A diaphragm reacts to pressure changes to move a push rod transversely against the midportion of the ribbons and deflect them into an arcuate configuration. Deflection of the ribbons moves the ball away from the valve seat. The push rod has a mechanical advantage with respect to movement of the ball. This mechanical advantage decreases with increased deflection of the ribbons. When the ball is in closed position engaging the valve seat, the ribbons buckle to provide an added mechanical advantage between movement of the push rod and movement of the ball.

United States Fatertt' [191 Whitten {45] Sept. 11, 1973 [22] Filed:

[ RIBBON TYPE FLOW CONTROL DEVICE David E. Whitten, Northridge, Calif.

[73] Assignee: Air-Dry Corporation of America,

Northridge, Calif.

Dec. 29, 1971 [21] Appl. No.: 213,669

[75] Inventor:

Primary Examiner-Arnold Rosenthal Attorney-Robert C. Comstock [57]ABSTRACT A ribbon type flow control device which provides a variablemechanical advantage. A ball type poppet is removably mounted in a valveseat. A pair of elongated flat resilient ribbons are connected at oneend thereof to the ball and fixed at the other end. A diaphragm reactsto pressure changes to move a push rod transversely against themidportion of the ribbons and deflect them into an arcuateconfiguration. Deflection of the ribbons moves the ball away from thevalve seat. The push rod has a mechanical advantage with respect tomovement of the ball. This mechanical advantage decreases with increaseddeflection of the ribbons.

, When the ball is in closed position engaging the valve seat, theribbons buckle to provide an added mechanical advantage between movementof the push rod and movement of the ball.

10 Claims, 10 Drawing Figures RIBBON TYPE FLOWCONTROI. DEVICE BACKGROUNDOF THE INVENTION 1. Field of the Invention:

The invention relates to a flow control device which can be used inliquid or pneumatic systems and in fluid controls such as regulators,relief valves, solenoid valves, on-off devices and other devices whichrequire or which can utilize a control mechanism which provides avariable mechanical advantage.

2. Description of the Prior Art:

A flow control device which utilizes hard poppet-seat interfaces,particularly metal-to-metal, requires a large force to seat the poppet.From the reseal or touch position to sealoff requires a seat stressproportionate to the degree of flatness and the asperities of thematerials used. In the case of regulators and relief valves, thecontrolled pressure inaccuracy is proportional to the amount of sealingforce. In the case of a simple direct acting regulator this seat stressreflects itself in a regulated pressure error inversely proportional tothe controller pressure sensing area. For a metal-to-metal poppet-seatdesign this pressure error can be significant.

Another problem is that destructive chatter can occur with small poppetstrokes and large pressure differential, due to Bernoulli effects.Poppet chatter is caused by fluid flow pressure variations on the poppetand seat, usually at small strokes due to effective poppet pressure areachanges. Seat-poppet chatter and instability occur at high inletpressures and low flow rates.

On the other hand, soft poppets and seats require less sealing force.They have other disadvantages, however, such as temPerature limitations(both hot and cold), fluid and contamination erosion which adverselyaffect their reliability and life, dimensional instability due to coldflow and limited fluid compatability.

A control device of the type now in use in relief valves in order toachieve results comparable to the present invention would requireextremely large sensing elements which would have the disadvantages ofexcessive size and weight. A comparable solenoid valve would likewiserequire an extremely large coil. A simple lever type of structure hasthe disadvantage of requiring large control strokes. Large controlstrokes require a low rate (vibration sensitive) controller spring andcorresponding increase in package size (clearances).

A high mechanical advantage is required when using a metal-to-metal seatand/or large. pressure sensing diaphragms, but if the same mechanicaladvantage were continued through the flow control stroke to full flow ormaximum opening, it would require an excessively long control stroke andwould result in an unacceptably large amount of regulated pressureerror.

I SUMMARY OF THE INVENTION The ideal solution for an all metal controldevice with minimum control pressure error is a control device which hasa very high mechanical advantage at lockup, a lesser but still highmechanical advantage for small poppet strokes to minimize chatter andinstability and a low mechanical advantage for medium to high flowregulation. It should also have a small controller stroke, to reduce thecontroller spring rate error and hysteredue to the center supporteffecting two shorter beams since the buckling load is inverselyproportionate to the square of the length.

After opening, with small poppet strokes, a large ribbon deflection isrequired to effect a small poppet stroke. This large mechanicaladvantage is desirable for accurate flow control and eliminates seatchatter especially with high inlet pressures. The mechanical advantagerapidly diminishes with ribbon deflection.

One of the primary objects of the present invention is to provide a flowcontrol device which affords a substantial amount of mechanicaladvantage which gives increased poppet-seat sealing force and easiercontrol with small poppet strokes.

A further object of the invention is to provide such a device in whichthis mechanical advantage decreases rapidly as the poppet leaves theseat.

A more particular object of the invention is to provide a structurethrough which a mechanical advantage such as approximately 30 to I canhe attained.0btaining a mechanical advantage of this order by means of asimple lever is either impractical or the mechanism would becomeexcessively large due to the minimum dimensions required between thefulcrum and poppet and the correspondingly increased dimensions of thelever. i

Another object of the invention is to provide a device of the typedescribed in which there are no friction or wear points on the ribbonbecause the ends are fixed.

A further object of the invention is. to provide a device of the typedescribed in which the desired mechanical advantage is accomplished bybending the ribbon to increase its arc and decrease its chord, thusopening the poppet.

It is amOng the objects of the invention to provide a flow controldevice which possesses the advantages and benefits set forth above anddescribed hereinafter in this specification.

Another object of the invention is to provide a flow control devicehaving a variable mechanical advantage.

My invention also comprises such other objects, advantages andcapabilities as willlater more fully appear and which are inherentlypossessed by my invention.

While I have shown in the accompanying drawings, a preferred embodimentof my invention, it should be understood that the same is susceptible ofmodification and change without departing from the spiritof the in--vention.

DESCRIPTION OF THE DRAWINGS FIG. 4 is a transverse sectional view takenalong line 44 of FIG. 2;

FIG. 5 is a partial sectional view similar to FIG. 2, but showing thedevice in open position;

FIG. 6 is a diagrammatic drawing of a conventional method of obtaining amechanical advantage by. a simand the valve seat 32 comprises the end ofa circular ple lever between a controller (pressure sensing element) anda flow control poppet;

FIG. 7 is a graph showing the linear relationship of controller strokeversus poppet stroke and constant mechanical advantage of a structure ofthe type shown in FIG. 6;

FIG. 8 is a diagrammatic drawing of thepresent invention in openposition, with the ribbon bowed;

FIG. 9 is a similar view with the poppet closed (lock v up) and theribbon buckled in an S shape to provide sealoff force;

FIG. 10 is a graph showing the non-linear relationship of controllerstroke versus poppet stroke and the resultant non-linear mechanicaladvantage provided by the present invention.

' DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment whichhas been selected to illustrate my invention comprises a bonnet 10,which is secured by a'bonnet ring 11 to a body 12 which encloses anelongated hollow tube 13. The bonnet 10 contains an adjusting screw 14which is vertically movable to adjust the position of a spring button 15disposed beneath the adjusting screw 14. An elongated adjusting spring16 extends between the button 15 and an inverted cup 17.

The cup 17 is mounted on the upper side of a resilient diaphragm 18,which extends transversely and is held at its periphery between thelower flange of the bonnet l0 and the body 12.

A hexagonal nut 19 which is disposed within the cup 17 is attached tothe upper end of a metallic button, the lower portion of which isdisposed beneath the diaphragm l8 and the upper portion of which extendsthrough the center of the diaphragm 18.

The upper end of a push-rod 20 is disposed in abutberyllium copperstrip, spring steel or other suitable material. The ribbons are securedat one end thereof to each other and to the tube 13 by a rivet 26. Theribbons 25 are secured at their opposite ends to each other and to thediametrically reduced inner end of a piston 27 by a rivet 28.

- The opposite end of the piston 27 carries a centrally disposed ballguide 29. The ball guide 29 has a ball socket 30 in which a ball 31 isrotatably mounted. The portion of the ball 31 remote from the ballsocket 30 engages a circular metallic valve seat 32 which is formed in aseat member 33 which extends transversely across one end of the tube 13.The seat member 33 has a flat face which is directed toward the ballguide 29 passage 42 formed in the center thereof. The valve seat 32extends through the seat member 33 and is slightly enlarged on the sideof the seat member 33 remote from the ball 31.

A transversly directed filter disc 34 is disposed outwardly from theseat member 33. The filter disc 34 and the seat member 33 are held inplace by an inlet fitting 35 which is threadedly attached to the end ofthe tube 13. The inlet fitting 35 is provided with an internallythreaded opening which is connected to the valve seat 32 through thefilter-disc 34.

A poppet spring 36 surrounds the inner end of the piston 27, the rivet'28 and the adjustment ends of the ribbons 25. One end of the poppetspring 36 engages the piston 27 while the other end engages a springretainer 37 which is held within the tube 13 by a back-up ring 38. v

A metallic spacer 39 is disposed between the ribbons 25 adjacent themidportion thereof directly beneath the push-rod 20. A semicircular leafspring 40 is attached at its center to the ribbons 25 by' a retainer 41which extends through the spring 40 and ribbons 25 and is outwardlyenlarged at its opposite ends. The leaf spring 40 has a pair of freeends which bear against the inner surface of the tube beneath and onopposite sides of the spacer'39.

FIG. 2 of the drawings shows the device in closed position, with theball 31 comprising the poppet and being firmly seated in the valve seat32. A decrease in the pressure within the tube l3'causes the diaphragm18 to be'deflected downwardly, moving the button 21 and push-rod 20downwardly. Downward movement of the push-rod 20 exerts downwardpressure against'the midportions of the ribbons 25, causing them to bedeflected and bent downwardly against the pressure of the leaf spring40.

As the ribbons 25 bend, they pull the piston 27 inwardly and slightlydownwardly, thereby pulling the ball 31 away from the valve seat 32 toallow fluid to flow through the inlet fitting 35 into the tube 13 andout through a transversely directed fluid outlet 43 .which connects withthe interior of the tube 13.

As the pressure within the tube 13 is increased, the diaphragm l8 flexesupwardly, pulling the button 21 and push-rod upwardly and relieving thedownward pressure on the midportions of the ribbons 25. The ribbons 25will return to a substantially straight position, moving the ball guide29 upwardly and outwardly to return the ball 30 to closed positionsealing off the valve seat 32 and cutting off the flow through inletfitting 35.

It is preferable that the device be so designed that at lockup orcomplete sealoff, the ribbons 25 will buckle in two pieces to form an S"shape. This is indicated schematically in FIG. 9 of the drawings. It hasnot been shown in'FIG. 2 because the amount of buckling is slight anddifficult to show in proper proportion.

The mechanical advantage provided by the ribbons 25 prior to buckling isapproximately lO/l. After buckling, the mechanical advantage isincreased to approximately 30/], due to the fact that the ribbons 25 arein effect converted into two short sections of one half the originallength. Since the buckling load is inversely proportional to the squareof the length, the mechanical advantage would in theory be increasedfour times. In practice, the result is approximately a three timesincrease.

It has been found that if the ball 31 and valve seat 32 are perfectlymatched and if all parts are smooth and dimensionally perfect, it ispossible to achieve a complete sealoff or lockup without buckling theribbons 25. The buckling provides added force, however, which assures acomplete sealoff under less than perfect conditions.

FIG. 6 of the drawings is a diagrammatic or schematic view showing aconventional method of obtaining a mechanical advantage by a simplelever between the control actuated by a pressure sensing element and aflow control poppet. In FIG. 6, the symbols represent the following: Xccontroller stroke, Xp poppet stroke, Lp length of controller lever, lplength of poppet lever, Lp/lp mechanical advantage, Pr outlet pressure,Ps inlet pressure.

It will be noted that obtaining a large mechanical advantage calls forLp to be as large as possible and/or for lp to be as small as possible.Making Lp larger presents problem of excessive size and weight. Making1p smaller presents problems of minimum achievable dimensions.

FIG. 7 is a graph showing the linear relationship between the controllerstroke and the poppet stroke in a conventional structure of the typeshown in FIG. 6. It will be noted that in this structure the mechanicaladvantage is a constant. I

FIG. 8 is a diagrammatic or schematic diagragm which illustrates thepresent invention, with the con-v troller depressed to bow the ribbonand open the poppet. In this diagragm,Xp (A L) =f(Xc). The poppetopening is equal to the length of the arc of the ribbons 25, less thelength of their chord. The poppet opening (Xp) is accordingly a functionof the controller stroke (Xc).

FIG. 9 is a diagrammatic view similar to FIG. 8 showing the poppet inclosed or lock up position, with the ribbon buckled into an S shape toprovide seal-off force. The buckling of the ribbon has been omitted fromFIG. 2 of the drawings for clarity of illustration.

FIG. 10 is a graph showing in one line the relationship between thecontroller and the valve opening. The other line shows the change inmechanical advantage as the valve is progressively opened. It will benoted that at first opening there is an extremely high mechanicaladvantage and a relatively large controller stroke will produce arelatively small poppet stroke. After the valve is opened further, themechanical advantage pro.- gressively decreases, so that a relativelysmaller controller stroke is then required to produce further opening ofthe poppet.

I claim:

1. A flow control device for a valve having a seat and a poppetremovably mounted in said valve seat for opening and closing said valve,said flow control device comprising at least one elongated resilientribbon, one end of said ribbon being connected to said poppet and theother end of said ribbon being fixed, said ribbon normally beingsubstantially straight and in longitudinal alignment with respect tosaid valve seat, control means extending transversely with respect tosaid ribbon, said control means being movable to engage said ribbonadjacent the midportion thereof and deflect said ribbon into an arcuateconfiguration, the deflection of said rib- .bon moving said poppet awayfrom said valve seat to open said valve, said ribbon being adapted toreturn to a substantially straight configuration to reseat said poppetupon the reverse movement of said control means, said control meanshaving a substantially large mechanical advantage with'respect to themovement of said poppet, said mechanical advantage decreasing with theincreased deflection of said ribbon by said control means, said ribbonbeing constructed and arranged to buckle at two places between itsmidportion and its opposite ends when said valve is closed, providing anincreased mechanical advantage between said control means and poppet.

2. The structure described in claim 1, said device including a pair ofparallel spaced ribbons. i y

3. The structure described in claim 1, and a piston carrying a ball,said piston connected to one end of said ribbon, a coil spring norrnallyurging said piston and ball toward said valve seat.

4. The structure described in claim 1, said piston being mounted foroutward tilting movement away from said valve seat upon the arcuatedeflection of said ribbon.

5. The structure described in claim 4, and second spring means disposedon the opposite side of said ribbon from said control means, said secondspring means urging said ribbon oppositely to said control means.

6. The structure described in claim 5, said second spring meanscomprising an elongated leaf spring having its midportion in engagementwith said ribbon opposite from said control means. I

7. The structure described in claim 6, and diaphragm meansconnected tosaid control means, said diaphragm .means being adapted to move saidcontrol means in response to changes in pressure on the opposite sidesof said diaphragm.

8. The structure described in claim 3, said device including a pair ofparallel spaced ribbons.

9. The structure described in claim 8, and a spacer disposed between themidportions of said ribbons.

10. The structure described in claim 6, said device including a pair ofparallel spaced ribbons, said leaf spring engaging the ribbon remotefrom said control means.

1. A flow control device for a valve having a seat and a poppetremovably mounted in said valve seat for opening and closing said valve,said flow control device comprising at least one elongated resilientribbon, one end of said ribbon being connected to said poppet and theother end of said ribbon being fixed, said ribbon normally beingsubstantially straight and in longitudinal alignment with respect tosaid valve seat, control means extending transversely with respect tosaid ribbon, said control means being movable to engage said ribbonadjacent the midportion thereof and deflect said ribbon into an arcuateconfiguration, the deflection of said ribbon moving said poppet awayfrom said valve seat to open said valve, said ribbon being adapted toreturn to a substantially straight configuration to reseat said poppetupon the reverse movement of said control means, said control meanshaving a substantially large mechanical advantage with respect to themovement of said poppet, said mechanical advantage decreasing with theincreased deflection of said ribbon by said control means, said ribbonbeing constructed and arranged to buckle at two places between itsmidportion and its opposite ends when said valve is closed, providing anincreased mechanical advantage between said control means and poppet. 2.The structure described in claim 1, said device including a pair ofparallel spaced ribbons.
 3. The structure described in claim 1, and apiston carrying a ball, said piston connected to one end of said ribbon,a coil spring normally urging said piston and ball toward said valveseat.
 4. The structure described in claim 1, said piston being mountedfor outward tilting movement away from said valve seat upon the arcuatedeflection of said ribbon.
 5. The structure described in claim 4, andsecond spring means disposed on the opposite side of said ribbon fromsaid control means, said second spring means urging said ribbonoppositely to said control means.
 6. The structure described in claim 5,said second spring means comprising an elongated leaf spring havingit''s midportion in engagement with said ribbon opposite from saidcontrol means.
 7. The structure described in claim 6, and diaphragmmeans connected to said control means, said diaphragm means beingadapted to move said control means in response to changes in pressure onthe opposite sides of said diaphragm.
 8. The structure described inclaim 3, said device including a pair of parallel spaced ribbons.
 9. Thestructure described in claim 8, and a spacer disposed between themidportions of said ribbons.
 10. The structure described in claim 6,said device including a pair of parallel spaced ribbons, said leafspring engaging the ribbon remote from said control means.